1. Field of the Invention
This invention relates to photography and, more particularly to an improved film advancing-fluid spreading apparatus for use with cameras of the self-developing type.
2. Description of the Prior Art
The prior art is replete with fluid-spreading apparatus for use with cameras of a self-developing type. A variety of forms of photographic apparatus has been proposed wherein each film unit included in an assemblage of a succession of individual photographic film units is moved, following exposure, between a pair of pressure-applying members for releasing a processing composition carried by the film units and distributes the processing composition within the film unit. Movement of successive photographic film units between the pressure-applying members is effected by manually pulling or drawing each film unit aided by a leader or similar element attached thereto. The film unit is advanced by positioning the pressure-applying members such that they function to receive a portion of the film unit therebetween whereupon the portion of the film unit is grasped and manually withdrawn between the pressure-applying members towards the exterior of the camera. While being essentially satisfactory, the apparatus necessitates a camera structure complicated by an inclusion of a requisite means for storing and manipulating a plurality of leaders such that each leader is made available on the exterior of the camera. A disadvantage inherent in this class of fluid spreading apparatus is a requirement that the photographic film unit be withdrawn from the camera between the pressure-applying members at a uniform rate and in a straight line whereby the processing composition is uniformly dispersed across a photosensitive layer of the assemblage. Failure to do so often results in an uneven spreading of the processing composition whereby portions of the exposed photosensitive layer not contacted thereby will remain undeveloped.
Another class of fluid spreading apparatus includes means for engaging the film unit near its trailing end and advancing the assemblage into the bite of a pair of non-rotating pressure-applying members as shown in U.S. Pat. Nos. 2,477,324 and 2,873,658. The major drawback with apparatus of the type set forth in these two patents is that the film unit used in U.S. Pat. No. 2,477,324 must be substantially rigid or thick in order to withstand pressures exerted thereon in moving the assemblage into the bite of the pressure-applying members, while the film unit in U.S. Pat. No. 2,873,658 must be substantially rigid or thick in order to enable the film unit to drive the pressure-applying members as the film unit is moving therebetween. Increasing the thickness and/or rigidity of the assemblage adds to material and manufacturing costs and in a case of increased thickness subtracts from compactness of a cassette wherein the assemblage of film units is retained and the camera wherein the cassette is adapted for use.
An advancement in fluid spreading apparatus has been introduced wherein the film unit is advanced and processed subsequent to exposure by a motorized system. The system automatically, upon receiving a signal that the film unit has been exposed within a camera, advances the exposed film unit into the bite of a pair of pressure-applying members adapted to receive the film unit and continues its movement at a uniform rate toward the camera's exterior while spreading a processing composition between elements of the film unit as shown in U.S. Pat. No. 3,776,118. A motor included in the system is connected by a gear train to one of the pair of pressure-applying members, thereby imparting rotary motion in a predetermined direction thereto and serves to advance the film unit between the pair of pressure-applying members to provide the film unit with complete coverage of the processing composition during a processing cycle. While serving to eliminate some of the undesirable features of the aforementioned fluid spreading apparatus, the sytem does not provide a convenient method for manually rotating the pressure-applying members whereby remnant deposits of the processing composition may be removed therefrom, or more importantly, for manually withdrawing the film unit between the pressure-applying members to complete the processing cycle which may have been interrupted by a malfunction of the motorized system whereby the film unit lies arrested between the pressure-applying members in a partially processed state. Manual rotation of the pressure-applying member may present an excessive loading condition to each member of the system including the motor due to the necessity to overcome a mechanical advantage provided in the system's design which becomes a mechanical disadvantage when energy is transmitted back through the system which could lead to extensive damage thereto.
From the foregoing, it can be seen that there is a need for a drive system for a fluid spreading apparatus having at least one rotatable pressure-applying member. wherein energy may be transmitted to the pressure-applying member to rotate it in a predetermined direction but which substantially prevents energy from being transmitted by rotation of the pressure-applying member back through the drive system.